bonnie will lead an army of handlers that will follow bonnie's every stroke to nourish, encourage, and protect her. >> fabulous. >> one of their biggest concerns, sharks. >> these are great waters for sharks. >> luke tipple is the team's lead shark diver. he knows just how dangerous these waters can be. >> you're watching this chum box that's hanging off the back of the boat. in these particular waters, we're looking for oceanic white tips, hammer heads, tiger sharks, caribbean reef sharks. this animal has evolved to dominate the ocean. they have a sixth sense. they can feel the electricity in the water. they know that we're there. >> and that's why in 1978 diana swam in a shark cage. today she just uses this. >> sharks are tremendously sensitive to this. this is actually in the kayak. >> it's called a shark shield. off the coast of the bahamas, tipple shows us how it works. it's a shark feeding frenzy at this block of chum until tipple approaches and turns on the shark shield that hangs right above it. now the device emits a strong but harmless signal that overwhelms the shark's sense